Formatting not updating
Excel has a “used range” for every sheet in your workbook, and the larger this is, the bigger the file size becomes.
For new files, the used range is only cell A1, but as you work through a file, it will increase to represent the rightmost column and furthest row that you’ve edited or formatted.
Especially in older files, even if cells are blank and have no formatting, Excel may be treating them within the used range, leading to a larger file size for no reason.
If formula calculation is slowing down your work, then go ahead and disable it.
Now, you might notice some strange behaviour when Manual is selected.
If you edit a cell containing a formula and press Enter, that formula will calculate as usual.
You can reduce the file size of your Excel workbook by unhiding all sheets, and checking if you still require that data or not.
I’ve hidden the best way to reduce file size down at position #3.